The conventional Public Switched Telephone Network (PSTN) is a circuit switched network in which calls are assigned dedicated circuits during the duration of the call. Such networks are well known in the art, and service providers have developed various services which may be provided to subscribers via such a conventional circuit switched network.
Recently, data packet networks, such as local area networks (LAN) and wide area networks (WAN) have become more prevalent. These data packet networks operate in accordance with the internet protocol (IP) and such networks are referred to as IP networks. The popularity of IP networks has created an interest in providing voice and related services over IP networks.
Conventional PSTN voice services dedicate a circuit connection between a calling and called party, and as such, that connection is guaranteed a certain level of performance because it is not shared with any other network users. IP networks, on the other hand, are shared networks in which the network resources are shared between users. The notion of a connection in a data packet network is very different from the notion of a connection in a circuit network. In a circuit network, the connection is a dedicated circuit which is used only by the calling and called parties. As such, it is easy to guarantee a certain level of service via the circuit network. The problem with such a network is that of efficiency. That is, the dedication of a circuit between all calling and called parties may be inefficient because such dedicated circuits provide more bandwidth than is necessary. In a data network, the connection between two parties is not dedicated, and traffic between the parties is transmitted via the data packet network along with the data packets of other users. There is no dedicated path between the parties, and data packets may be transmitted between the parties via different paths, depending upon network traffic.
In the PSTN, call setup is controlled by a signaling network in accordance with the well known Signaling System No. 7 (SS7). An SS7 network exists within the PSTN network and controls call setup by conveying labeled messages via signaling channels which are separate from the voice channels. The details of an SS7 network is well known and the details will not be described in further detail herein.
Signaling in a voice over IP (VoIP) network is accomplished by sending messages utilizing the Session Initiation Protocol (SIP) which will be described in further detail below. In contrast to the SS7 network utilized in the conventional PSTN network, SIP messages in a VoIP network are not transmitted via a dedicated signaling network, but are transmitted like any other data packets.
One of the goals of a voice network is to minimize post dial delay (PDD) which is the time required to connect the call after the user finishes dialing the called number. One of the factors that determines the PDD is the extent of signaling required to set up the call. Thus, a reduction in the required signaling will decrease the PDD and therefore increase customer satisfaction. Another goal of a voice network is to decrease the load on the various network elements. Once again, a reduction in the required signaling also reduces the load on the network signaling elements.
Therefore, what is needed is a method and apparatus for reducing the required signaling in a VoIP network.